Growth hormone is an anabolic hormone capable of promoting linear growth, weight gain and whole body nitrogen retention in animals. Growth hormone is produced in somatotroph cells of the anterior pituitary gland of animals and secreted throughout life. It is mainly controlled in the brain by two hypothalamic peptides: growth hormone releasing hormone (GHRH), which stimulates its secretion and synthesis; and somatostatin, which inhibits them. In human beings and other mammals, regulated expression of the growth hormone pathway is considered essential for optimal linear growth, as well as homeostasis of carbohydrate, protein and fat metabolism.
As canines age, their growth hormone levels decrease considerably resulting in a loss of skeletal muscle mass, osteoporosis, increased fat deposition, decreased lean body mass, and other disorders. Studies in human beings and other mammals have demonstrated that the recombinant growth hormone therapy may address the reduction of growth hormone. However, the recombinant growth hormone therapy for canines is limited and has proved to be inefficient.
U.S. Pat. No. 7,361,642, issued on Apr. 22, 2008 to Draghia-Akli, discloses a method for increasing growth hormone in canines. A canine-specific growth hormone releasing hormone (dGHRH) or a nucleic acid molecule that encodes the dGHRH is administered to canines to increase the level of growth hormone secretion. The canines treated with specific growth hormone releasing hormone show increased insulin-like growth factor I, enhanced red blood cells production and hemoglobin concentration, and improved protein metabolism.
Journal of Orthopedic Research 15:519-527 (1997) discloses that a growth hormone secretagogue, MK-0677, elevates levels of serum insulin-like growth factor-I in canines, which in turn increases the size and strength of the quadriceps muscle in canines during remobilization.
U.S. Publication No. 2008/0119819, published on May 22, 2008 to Hojby, discloses that an administration of growth hormone enhances bone growth factors and fracture healing in canines.
It has also been reported that for adult canines of both sexes, exogenous growth hormone induces a marked increase in new bone formation. (Calcified Tissue Research 10(1):1-13 (1972)).
Other studies have shown that in the canines that were given growth hormone, the quantity of protein in the blood plasma is increased, and the plasma protein pattern is altered. (Endocrinology 53: 134-162 (1953)). Additionally, it is known that growth hormone treatment improves protein metabolism in canines.